Innovations in Condition Monitoring – Broken Rotor Bar Detection using Numerical Relay

Malcolm Ballinger
Asset Manager Electrical 

Peter Burnell
Electrical Engineer

AGL Torrens Island Power Station

In 2015 AGL Torrens identified a 3.3MW DOL induction motor as a high risk machine, based on site testing results of high offline partial discharge and DLA results.  The reason for the high results was not known.  In 2017 the motor failed due to broken rotor bars coming loose and contacting the stator windings.  The procurement of a spare motor had been planned, but due to constraints and other priorities, the motor failed before it could be procured. 

The failure was a large unbudgeted repair cost and caused an extended period of redundancy loss.  The type of fault is typical of the make of machine, with the station itself having a history of half a dozen similar type of failures.  The challenge for the asset engineering team is to be able to more definitively correlate poor HV test results to the condition of the machine, with the goal to be able to prioritise contingency plans.

AGL Torrens has investigated additional online condition monitoring technology, including market reviews, university laboratory experimentation, inhouse bench testing, and ultimately installation of advanced protection relays and hardware to detect rotor bar failures.  This paper describes the investigation process and the results obtained.

Malcolm is a Chartered Professional Engineer with fifteen years of experience as an engineering consultant, a site based EPC construction engineer, and as an asset owner.  He holds a 1st class honours degree in Electrical and Electronic Engineering from the University of Canterbury New Zealand.  He has worked in various locations in Australia, the United Kingdom and China.  Malcolm has a broad range of experience in engineering design, construction activities, and plant operation reviews.  Since 2012, as the Asset Manager Electrical at AGL Torrens Island Power Station, Malcolm has been responsible for the safe and reliable operation of all rotating and stationary electrical plant.

Peter is a Chartered Professional Electrical Engineer with nine years of power industry experience. He holds a first class honours degree in Electrical and Electronic Engineering from the University of Adelaide. From working for an engineering consultancy, Peter has obtained a broad range of skills and experiences and has worked for a range of companies including utilities, generators and mining companies. He has also developed specific skills in the area of power system protection having worked in this area for a distribution utility. More recently Peter has become a power station electrical engineer and is responsible for running projects to ensure the safe and reliable operation of the station.